In a known eye fundus camera of this type, the illuminating system is provided with one or more annular apertures, through which light emitted from the light source is directed toward the eye fundus. The apertures are positioned such that their images are formed in the anterior part of the eye, and they limit the bundle of rays of light directed toward the fundus such that it does not overlap at the cornea or at the crystalline lens another bundle of rays of light which is reflected or scattered from the fundus and which is to be received by the photographing system. In this way, the known eye fundus camera is capable of escaping such detrimental reflection or scattering of light at the cornea or the crystalline lens as causes part of the light for illumination to travel back from the cornea or the crystalline lens into the photographing system.
In order to escape the detrimental reflection or scattering effectively, the diameters of the annular apertures must be made larger as the angle of view of the camera is made wider, or as the image magnification is made smaller. For this reason, in the case of a variable image-magnification eye fundus camera in which the angle of view is variable with the image magnification, the diameters of the annular images of the apertures in the anterior part of the eye, or the diameter of the annular cross section of the illuminating light ray bundle, must be large, as compared with those or that of an eye fundus camera with a fixed narrow angle of view, so as to escape the detrimental reflection or scattering of light to make a clear photograph of the eye fundus throughout the whole range of angle of view.
Thus, in the case of a person, such as an aged person or a diabetes mellitus patient, who cannot open the irises wide sufficiently, the eye fundus may be photographed with an eye fundus camera with a fixed narrow angle of view. A variable image-magnification eye fundus camera, however, cannot be used to make a photograph of such person's eye fundus, because the light directed to the eye is interrupted by the iris irrespectively of the angle of view.
It is thus an object of the present invention to provide an eye fundus camera of the type in which the angle of view is variable with the image-magnification, and in which the illuminating system is improved so that a sharp photograph can be taken at a narrow angle of view even if the pupil of the eye to be inspected is relatively reduced.
It is another object of the present invention to provide an eye fundus camera having an illuminating system which is improved so that the detrimental reflection or scattering of light as mentioned hereinabove can be avoided and thus a clear image of the eye fundus can be obtained throughout a wide range of angle of view.